I don't have IBS, but I can sympathize to some degree -- most of my anemia meds are known for giving people "the runs." I will spare you any more details.
What's weird for me is that several weeks ago, when my white count was pretty low, they told me to stay away from fresh fruits and vegetables. So I went a week without them, even though I had all this great fresh food in my fridge.
Next week, my white count was fine, and I was so happy, I came home and had a huge salad with a ton of vegetables in it, and an orange for dessert. I have had "the runs" ever since. Every time now that I eat a fruit or vegetable, I am on the pot in about 30 seconds.
Blah. It's no fun, I know!
Candy